Systems and methods for monitoring selected terrestrially used satellite frequency signals to reduce potential interference

ABSTRACT

A satellite radiotelephone frequency band can be reused terrestrially by an ancillary terrestrial network even within the same satellite cell, using interference reduction/cancellation techniques. An interference reducer is responsive to a space-based component and to an ancillary terrestrial network. The interference reducer is configured to reduce interference in wireless communications that are received by the space-based component from first radiotelephones in the satellite footprint over a satellite radiotelephone frequency band using wireless communications that are received by the ancillary terrestrial network from selected ones of second radiotelephones in the satellite footprint over the satellite radiotelephone frequency band and/or wireless communications that are transmitted by the ancillary terrestrial network to the second radiotelephones in the satellite footprint over the satellite radiotelephone frequency band. The interference reducer may include a prefilter that is configured to determine the selected ones of the second radiotelephones.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/133,102,filed May 19, 2005, now U.S. Pat. No. 7,447,501 entitled Systems andMethods for Monitoring Selected Terrestrially Used Satellite FrequencySignals to Reduce Potential Interference, and claims the benefit ofprovisional Application No. 60/573,991, filed May 24, 2004, entitledSystems and Methods for Monitoring Selected Terrestrially ReusedSatellite Frequency Signals to Reduce Potential Interference andprovisional Application No. 60/598,975, filed Aug. 5, 2004, entitledSystems and Methods for Monitoring Terrestrially Reused SatelliteFrequency Signals to Reduce Potential Interference. This applicationalso is a continuation-in-part of application Ser. No. 10/225,616, filedAug. 22, 2002 (now U.S. Pat. No. 7,031,702), entitled Additional Systemsand Methods For Monitoring Terrestrially Reused Satellite Frequencies ToReduce Potential Interference, which claims the benefit of provisionalApplication No. 60/392,754, filed Jul. 1, 2002, entitled AdditionalSystems and Methods for Monitoring Terrestrially Reused SatelliteFrequencies to Reduce Potential Interference, and which is itself acontinuation-in-part of application Ser. No. 10/156,363, filed May 28,2002 (now U.S. Pat. No. 7,039,400), entitled Systems and Methods ForMonitoring Terrestrially Reused Satellite Frequencies To ReducePotential Interference, which claims the benefit of provisionalApplication No. 60/347,174, filed Jan. 9, 2002, entitled MonitoringTerrestrially Reused Satellite Frequencies to Reduce PotentialInterference, and which is itself a continuation-in-part of applicationSer. No. 10/074,097, filed Feb. 12, 2002 (now U.S. Pat. No. 6,684,057),entitled Systems and Methods for Terrestrial Reuse of Cellular SatelliteFrequency Spectrum, which claims the benefit of provisional ApplicationNo. 60/322,240, filed Sep. 14, 2001, entitled Systems and Methods forTerrestrial Re-Use of Mobile Satellite Spectrum. All of theabove-mentioned applications are assigned to the assignee of the presentapplication, the disclosures of all of which are hereby incorporatedherein by reference in their entirety as if set forth fully herein.

FIELD OF THE INVENTION

This invention relates to radiotelephone communications systems andmethods, and more particularly to terrestrial cellular and satellitecellular radiotelephone communications systems and methods.

BACKGROUND OF THE INVENTION

Satellite radiotelephone communications systems and methods are widelyused for radiotelephone communications. Satellite radiotelephonecommunications systems and methods generally employ at least onespace-based component, such as one or more satellites, that is/areconfigured to wirelessly communicate with a plurality of satelliteradiotelephones.

A satellite radiotelephone communications system or method may utilize asingle antenna pattern (beam) covering an entire area served by thesystem. Alternatively, in cellular satellite radiotelephonecommunications systems and methods, multiple antenna patterns (beams orcells) are provided, each of which can serve substantially distinctgeographical areas in the overall service region, to collectively servean overall satellite footprint. Thus, a cellular architecture similar tothat used in conventional terrestrial cellular radiotelephone systemsand methods can be implemented in cellular satellite-based systems andmethods. The satellite typically communicates with radiotelephones overa bidirectional communications pathway, with radiotelephonecommunications signals being communicated from the satellite to theradiotelephone over a downlink or forward link, and from theradiotelephone to the satellite over an uplink or return link.

The overall design and operation of cellular satellite radiotelephonesystems and methods are well known to those having skill in the art, andneed not be described further herein. Moreover, as used herein, the term“radiotelephone” includes cellular and/or satellite radiotelephones withor without a multi-line display; Personal Communications System (PCS)terminals that may combine a radiotelephone with data processing,facsimile and/or data communications capabilities; Personal DigitalAssistants (PDA) that can include a radio frequency transceiver and/or apager, Internet/Intranet access, Web browser, organizer, calendar and/ora global positioning system (GPS) receiver; and/or conventional laptopand/or palmtop computers or other appliances, which include a radiofrequency transceiver. A radiotelephone also may be referred to hereinas a “radioterminal”, a “wireless terminal” or simply as a “terminal”.As used herein, the term(s) “radiotelephone”, “radioterminal”, “wirelessterminal” and/or “terminal” also include(s) any other radiating userdevice/equipment/source that may have time-varying or fixed geographiccoordinates and/or may be portable, transportable, installed in avehicle (aeronautical, maritime, or land-based) and/or situated and/orconfigured to operate locally and/or in a distributed fashion over oneor more terrestrial and/or extra-terrestrial location(s).

Terrestrial networks can enhance cellular satellite radiotelephonesystem availability, efficiency and/or economic viability byterrestrially using at least some of the frequency bands that areallocated to cellular satellite radiotelephone systems. In particular,it is known that it may be difficult for cellular satelliteradiotelephone systems to reliably serve densely populated areas,because the satellite signal may be blocked by high-rise structuresand/or may not penetrate into buildings. As a result, the satellitespectrum may be underutilized or unutilized in such areas. Theterrestrial use of at least some of the satellite system frequencies canreduce or eliminate this potential problem.

Moreover, the capacity of the overall system may be increased by theintroduction of terrestrial frequency use of the satellite systemfrequencies, since terrestrial frequency use may be much denser thanthat of a satellite-only system. In fact, capacity may be enhanced whereit may be mostly needed, i.e., in densely populatedurban/industrial/commercial areas. As a result, the overall system maybecome more economically viable, as it may be able to serve moreeffectively and reliably a larger subscriber base.

One example of terrestrial use of satellite frequencies is described inU.S. Pat. No. 5,937,332 to the present inventor Karabinis entitledSatellite Telecommunications Repeaters and Retransmission Methods, thedisclosure of which is hereby incorporated herein by reference in itsentirety as if set forth fully herein. As described therein, satellitetelecommunications repeaters are provided which receive, amplify, andlocally retransmit the downlink signal received from a satellite therebyincreasing the effective downlink margin in the vicinity of thesatellite telecommunications repeaters and allowing an increase in thepenetration of uplink and downlink signals into buildings, foliage,transportation vehicles, and other objects which can reduce link margin.Both portable and non-portable repeaters are provided. See the abstractof U.S. Pat. No. 5,937,332.

Satellite radiotelephones for a satellite radiotelephone system ormethod having a terrestrial communications capability by terrestriallyusing at least some of the same satellite frequency band and usingsubstantially the same air interface for both terrestrial and satellitecommunications may be cost effective and/or aesthetically appealing.Conventional dual band/dual mode radiotelephone alternatives, such asthe well known Thuraya, Iridium and/or Globalstar dual modesatellite/terrestrial radiotelephones, duplicate some components (as aresult of the different frequency bands and/or air interface protocolsbetween satellite and terrestrial communications), which leads toincreased cost, size and/or weight of the radiotelephone. See U.S. Pat.No. 6,052,560 to the present inventor Karabinis, entitled SatelliteSystem Utilizing a Plurality of Air Interface Standards and MethodEmploying Same.

Satellite radioterminal communications systems and methods that mayemploy terrestrial use of satellite frequencies are described in U.S.Pat. Nos. 6,684,057 to Karabinis, entitled Systems and Methods forTerrestrial Reuse of Cellular Satellite Frequency Spectrum; 6,785,543 toKarabinis, entitled Filters for Combined Radiotelephone/GPS Terminals;6,856,787 to Karabinis, entitled Wireless Communications Systems andMethods Using Satellite-Linked Remote Terminal Interface Subsystems;6,859,652 to Karabinis et al., entitled Integrated or Autonomous Systemand Method of Satellite-Terrestrial Frequency Reuse Using SignalAttenuation and/or Blockage, Dynamic Assignment of Frequencies and/orHysteresis; and 6,879,829 to Dutta et al., entitled Systems and Methodsfor Handover Between Space Based and Terrestrial RadioterminalCommunications, and For Monitoring Terrestrially Reused SatelliteFrequencies At a Radioterminal to Reduce Potential Interference; andPublished U.S. Patent Application Nos. US 2003/0054761 to Karabinis,entitled Spatial Guardbands for Terrestrial Reuse of SatelliteFrequencies; US 2003/0054814 to Karabinis et al., entitled Systems andMethods for Monitoring Terrestrially Reused Satellite Frequencies toReduce Potential Interference; US 2003/0073436 to Karabinis et al.,entitled Additional Systems and Methods for Monitoring TerrestriallyReused Satellite Frequencies to Reduce Potential Interference; US2003/0054762 to Karabinis, entitled Multi-Band/Multi-Mode SatelliteRadiotelephone Communications Systems and Methods; US 2003/0224785 toKarabinis, entitled Systems and Methods for Reducing Satellite FeederLink Bandwidth/Carriers In Cellular Satellite Systems; US 2002/0041575to Karabinis et al., entitled Coordinated Satellite-TerrestrialFrequency Reuse; US 2003/0068978 to Karabinis et al., entitledSpace-Based Network Architectures for Satellite Radiotelephone Systems;US 2003/0153308 to Karabinis, entitled Staggered Sectorization forTerrestrial Reuse of Satellite Frequencies; and US 2003/0054815 toKarabinis, entitled Methods and Systems for Modifying Satellite AntennaCell Patterns In Response to Terrestrial Reuse of Satellite Frequencies,all of which are assigned to the assignee of the present invention, thedisclosures of all of which are hereby incorporated herein by referencein their entirety as if set forth fully herein.

Some satellite radiotelephone systems and methods may employinterference cancellation techniques to allow terrestrial use ofsatellite frequencies. For example, as described in U.S. Pat. No.6,684,057 to Karabinis, cited above, a satellite radiotelephonefrequency can be reused terrestrially by an ancillary terrestrialnetwork even within the same satellite cell, using interferencecancellation techniques. Moreover, the ancillary terrestrial network canuse a modified range of satellite band forward link frequencies fortransmission, to reduce interference with out-of-band receivers. Amodified range of satellite band forward link frequencies that is usedby the ancillary terrestrial network can include only a subset of thestandard satellite band forward link frequencies to provide a guardband, can include power levels that monotonically decrease as a functionof increasing frequency and/or can include two or more contiguous slotsper frame that are left unoccupied and/or are transmitted at reducedmaximum power. Time division duplex operation of the ancillaryterrestrial network may also be provided over at least a portion ofsatellite band return frequencies. Full or partial reverse modeoperation of the ancillary terrestrial network also may be provided,where at least some of the forward link and return link frequencies areinterchanged with the conventional satellite forward link and reverselink frequencies. See the Abstract of U.S. Pat. No. 6,684,057.

Other radiotelephone systems and methods can monitor terrestrial use ofsatellite-band frequencies to reduce potential interference. Forexample, as described in Published U.S. Patent Application No. US2003/0054814 A1, cited above, radiation by an ancillary terrestrialnetwork, and/or satellite radiotelephones that communicate therewith aremonitored and controlled, to reduce and preferably prevent intra-systeminterference and/or interference with other satellite radiotelephonesystems. In particular, a satellite radiotelephone system includes aspace-based component that is configured to wirelessly communicate withfirst radiotelephones in a satellite footprint over a satelliteradiotelephone frequency band, and an ancillary terrestrial network thatis configured to wirelessly communicate with second radiotelephones inthe satellite footprint over at least some of the satelliteradiotelephone frequency band, to thereby terrestrially reuse the atleast some of the satellite radiotelephone frequency band. Wirelessradiation by the ancillary terrestrial network and/or the secondradiotelephones at the space-based component is monitored, and theradiation by the ancillary terrestrial network and/or the plurality ofsecond radiotelephones is adjusted in response to the monitoring.Intra-system interference and/or interference with other satellitesystems thereby may be reduced or prevented. See the Abstract of U.S.Published Patent Application US 2003/0054814 A1.

Finally, additional systems and methods may be used to monitorterrestrially used satellite frequencies to reduce potentialinterference. For example, as described in Published U.S. PatentApplication No. US 2003/0073436 A1, cited above, a satelliteradiotelephone system includes a space-based component, an ancillaryterrestrial network, a monitor and a controller. The space-basedcomponent is configured to wirelessly communicate with radiotelephonesin a satellite footprint over a satellite radiotelephone frequency band.The satellite footprint is divided into satellite cells in which subsetsof the satellite radiotelephone frequency band are spatially reused in aspatial reuse pattern. The ancillary terrestrial network is configuredto wirelessly communicate with radiotelephones in the satellitefootprint over at least some of the satellite radiotelephone frequencyband, to thereby terrestrially reuse the at least some of the satelliteradiotelephone frequency band. The monitor is configured to monitorwireless radiation at the space-based component that is produced by theancillary terrestrial network and/or the radiotelephones in satellitecells that adjoin a satellite cell and/or in the satellite cell, in atleast part of the subset of the satellite radiotelephone frequency bandthat is assigned to the satellite cell for space-based componentcommunications. The controller is configured to adjust the radiation bythe ancillary terrestrial network and/or the radiotelephones, inresponse to the monitor. See the Abstract of U.S. Published PatentApplication U.S. 2003/0073436 A1.

SUMMARY OF THE INVENTION

Some embodiments of the present invention monitor selectiveterrestrially used satellite frequency signals to reduce potentialinterference. In particular, a satellite radiotelephone system accordingto some embodiments of the present invention includes a space-basedcomponent that is configured to receive wireless communications from aplurality of first radiotelephones in a satellite footprint over asatellite radiotelephone frequency band. An ancillary terrestrialnetwork is configured to receive wireless communications from aplurality of second radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band. The space-based component alsoreceives the wireless communications from the second radiotelephonesand/or the ancillary terrestrial network in the satellite footprint overthe satellite radiotelephone frequency band as interference, along withthe wireless communications that are received from the firstradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band. An interference reducer is responsive tothe space-based component and to the ancillary terrestrial network. Theinterference reducer is configured to reduce the interference in thewireless communications that are received by the space-based componentfrom the first radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band, using the wirelesscommunications that are received by the ancillary terrestrial networkfrom selected ones of the second radiotelephones in the satellitefootprint over the satellite radiotelephone frequency band and/or thewireless communications that are transmitted from the ancillaryterrestrial network to at least some of the second radiotelephones.

In some embodiments, the interference reducer comprises a prefilter thatis configured to determine the selected ones of the secondradiotelephones. In some embodiments, the prefilter is configured todetermine the selected ones of the second radiotelephones based on ameasure of signal strength received by the plurality of secondradiotelephones from the space-based component. In other embodiments,the prefilter is configured to determine the selected ones of the secondradiotelephones based on a random/pseudo-random selection, a percentageof the plurality of second radiotelephones, a geographic location of thesecond radiotelephones and/or a likelihood that the emissions of thesecond radiotelephones will cause interference with the wirelesscommunications that are received by the space-based component from thefirst radiotelephone(s). In some embodiments, the prefilter isconfigured to determine the selected ones of the second radiotelephonesbased on a measure of signal strength received by the plurality ofsecond radiotelephones from the space-based component exceeding athreshold.

In some embodiments, the second radiotelephones are configured totransmit to the ancillary terrestrial network and/or to the space-basedcomponent, the measure of signal strength received from the space-basedcomponent.

In other embodiments, the ancillary terrestrial network is configured totransmit to the interference reducer a measure of the wireless signalsreceived from one or more second radiotelephones, before and/or afterdemodulation, de-spreading and/or regeneration by the ancillaryterrestrial network and/or to transmit to the interference reducer ameasure of the wireless signals transmitted by the ancillary terrestrialnetwork to at least some of the second radiotelephones before and/orafter modulation and/or spreading. In some embodiments, the interferencereducer and/or another system element is configured to re-modulateand/or re-spread the measure of the wireless signals received from theancillary terrestrial network before being used by the interferencereducer. In some embodiments, the interference reducer and/or the othersystem element is/are configured to re-modulate and/or re-spread themeasure of the wireless signals received from the ancillary terrestrialnetwork to form a modulated and/or spread-spectrum chip-level signal.

In some embodiments of the present invention, the ancillary terrestrialnetwork is closer to the second radiotelephones than to the space-basedcomponent, such that the wireless communications from the secondradiotelephones are received by the ancillary terrestrial network priorto reception by the space-based component. The interference reducer isconfigured to generate at least one delayed replica of the wirelesscommunications from the selected ones of the second radiotelephones thatare received by the ancillary terrestrial network and to subtract thedelayed replica of the wireless communications of the selected ones ofthe second radiotelephones that are received by the ancillaryterrestrial network from the wireless communications that are receivedfrom the space-based component. In some embodiments, the interferencereducer comprises an adaptive interference canceller. Moreover, in someembodiments, the interference reducer is at least partially included inthe satellite gateway.

It will be understood by those having skill in the art that the aboveembodiments have been described primarily with respect to satelliteradiotelephone systems. However, other embodiments of the presentinvention can provide components of a satellite radiotelephone systemsuch as a gateway, a prefiltering unit, radiotelephones and/or anancillary terrestrial network. Moreover, analogous method embodimentsalso may be provided according to other embodiments of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of cellular radiotelephone systems,methods and components according to exemplary embodiments of the presentinvention.

FIG. 2 is a block diagram of adaptive interference reducers according toexemplary embodiments of the present invention.

FIG. 3 is a flowchart of operations that may be performed by aninterference reducer, such as the interference reducer of FIGS. 1 and/or2 according to exemplary embodiments of the present invention.

FIG. 4 is a flowchart of operations that may be performed by aprefilter, such as a prefilter of FIG. 3, according to exemplaryembodiments of the present invention.

DETAILED DESCRIPTION

Specific exemplary embodiments of the invention now will be describedwith reference to the accompanying drawings. This invention may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the invention to thoseskilled in the art. In the drawings, like designations refer to likeelements. It will be understood that when an element is referred to asbeing “connected”, “coupled” or “responsive” to another element, it canbe directly connected, coupled or responsive to the other element orintervening elements may be present. Furthermore, “connected”, “coupled”or “responsive” as used herein may include wirelessly connected, coupledor responsive.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless expressly stated otherwise. Itwill be further understood that the terms “includes,” “comprises,”“including” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as conunonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

It will be understood that although the terms first and second may beused herein to describe various elements, these elements should not belimited by these terms. These terms are only used to distinguish oneelement from another element. Thus, a first radiotelephone below couldbe termed a second radiotelephone, and similarly, a secondradiotelephone may be termed a first radiotelephone without departingfrom the teachings of the present invention. As used herein, the term“and/or” includes any and all combinations of one or more of theassociated listed items. The symbol “/” is also used as a shorthandnotation for “and/or”.

Moreover, as used herein, “substantially the same” band(s) means thattwo or more bands being compared substantially overlap in frequency, butthat there may be some areas of non-overlap, for example at a bandend(s). “Substantially the same” air interface(s) means that two or moreair interfaces being compared are similar but need not be identical.Some differences may exist in one air interface (i.e., a satellite airinterface) relative to another (i.e., a terrestrial air interface) toaccount for and/or accommodate different characteristics that may existbetween, for example, a terrestrial and satellite communicationsenvironments. For example, a different vocoder rate may be used forsatellite communications compared to the vocoder rate that may be usedfor terrestrial communications (i.e., for terrestrial communications,voice may be compressed (“vocoded”) to approximately 9 to 13 kbps,whereas for satellite communications a vocoder rate of 2 to 4 kbps, forexample, may be used); a different forward error correction coding,different interleaving depth, and/or different spread-spectrum codes mayalso be used, for example, for satellite communications compared to thecoding, interleaving depth, and/or spread spectrum codes (i.e., Walshcodes, long codes, and/or frequency hopping codes) that may be used forterrestrial communications.

FIG. 1 is a schematic diagram of cellular satellite radiotelephone (orradioterminal) systems, methods and components according to variousexemplary embodiments of the invention. As shown in FIG. 1, thesecellular satellite radiotelephone systems and methods 100 include atleast one Space-Based Component (SBC) 110, such as a satellite. Thespace-based component 110 may be configured to transmit wirelesscommunications to a plurality of radiotelephones 120 a in a satellitefootprint comprising one or more satellite radiotelephone cells,indicated in FIG. 1 by 130-130″″, over one or more satelliteradiotelephone forward service link (downlink) frequencies f_(D). Thespace-based component 110 may also be configured to receive wirelesscommunications from, for example, a first radiotelephone 120 a, in thesatellite radiotelephone cell 130, over a satellite radiotelephonereturn service link (uplink) frequency or frequencies f_(U). Anancillary terrestrial network, comprising at least one ancillaryterrestrial component 140, which may include an antenna 140 a and anelectronics system 140 b, is configured to receive wirelesscommunications from, for example, a second radiotelephone 120 b in theradiotelephone cell 130 over the satellite radiotelephone uplinkfrequency, denoted f_(U), which may be the same as f_(U). Thus, asillustrated in FIG. 1, radiotelephone 120 a may be communicating withthe space-based component 110 while radiotelephone 120 b may becommunicating with the ancillary terrestrial component 140. As shown inFIG. 1, the space-based component 110 also undesirably receives at leastsome of the wireless communications from the second radiotelephone 120 bin the satellite radiotelephone cell 130 over the satelliteradiotelephone frequency f′_(U) as interference. More specifically, apotential interference path is shown at 150. In this potentialinterference path 150, the return link signal of the secondradiotelephone 120 b at carrier frequency f′_(U) interferes withsatellite communications. This interference would generally be strongestwhen f′_(U)=f_(U), because, in that case, the same return link frequencywould be used for space-based component and ancillary terrestrialcomponent communications over the same satellite radiotelephone cell(intra-satellite cell frequency reuse by the ancillary terrestrialcomponent), and no spatial discrimination between satelliteradiotelephone cells would appear to exist.

Still referring to FIG. 1, embodiments of satellite radiotelephonesystems/methods 100 can include at least one gateway 160 that caninclude an antenna 160 a and an electronics system 160 b that can beconnected to other networks 162 including terrestrial and/or otherradiotelephone networks. The gateway 160 also communicates with thespace-based component 110 over a satellite feeder link 112. The gateway160 also communicates with the ancillary terrestrial component 140,generally over a terrestrial link 142.

Still referring to FIG. 1, an Interference Reducer (IR) 170 a also maybe provided at least partially in the ancillary terrestrial componentelectronics system 140 b. Alternatively or additionally, an interferencereducer 170 b may be provided at least partially in the gatewayelectronics system 160 b. In yet other alternatives, the interferencereducer may be provided at least partially in other components of thecellular satellite system/method 100 instead of or in addition to theinterference reducer 170 a and/or 170 b. The interference reducer isresponsive to the space-based component 110 and to the ancillaryterrestrial component 140, and is configured to reduce the interferencefrom the wireless communications that are received by the space-basedcomponent 110 and is at least partially generated by the transmissionsof the second radiotelephone 120 b to the ancillary terrestrialcomponent 140 in the satellite radiotelephone cell 130 over thesatellite radiotelephone frequency f′_(U) and/or by the transmissions ofthe ancillary terrestrial component 140 to the second radiotelephone 120b. The interference reducer 170 a and/or 170 b uses a measure of thewireless communications that are transmitted by the secondradiotelephone 120 b, intended for the ancillary terrestrial component140, in the satellite radiotelephone cell 130 using the satelliteradiotelephone frequency f′_(U) and/or a measure of the wirelesscommunications that are transmitted by the ancillary terrestrialcomponent 140 intended for the second radiotelephone 120 b to reduce theinterference from the wireless communications that are received by thespace-based component 110.

In embodiments of FIG. 1, the ancillary terrestrial component 140 isphysically closer to the first and second radiotelephones 120 a and 120b, respectively, than is the space-based component 110, such that thewireless communications from the second radiotelephone 120 b arereceived by the ancillary terrestrial component 140 prior to beingreceived by the space-based component 110. The interference reducer 170a and/or 170 b is configured to generate an interference reductionsignal comprising, for example, a measure of at least one delayedreplica of the wireless communications from the second radiotelephone(s)120 b that are received by the ancillary terrestrial component 140and/or a measure of at least one delayed replica of the wirelesscommunications that are transmitted by the ancillary terrestrialcomponent 140 to at least some of the second radiotelephones 120 b andto subtract the measure of the at least one delayed replica of thewireless communications from the second radiotelephone(s) 120 b that arereceived by the ancillary terrestrial component 140 and/or the measureof the at least one delayed replica of the wireless communications thatare transmitted by the ancillary terrestrial component 140 to the atleast some of the second radiotelephones 120 b from the wirelesscommunications that are received from the space-based component 110.Elements of the interference reduction signal(s) may be transmitted fromthe ancillary terrestrial component 140 to the gateway 160 and/orinterference reducer 170 b over link 142 and/or any other link.

Thus, adaptive interference reduction techniques may be used to at leastpartially cancel the interfering signal so that the same, or other,satellite radiotelephone uplink frequency can be used in a given cellfor communications by radiotelephones 120 with the satellite 110 andwith the ancillary terrestrial component 140. Accordingly, in someembodiments, all frequencies that are assigned to a given cell 130 maybe used for both radiotelephone 120 communications with the space-basedcomponent 110 and with the ancillary terrestrial component 140. In otherembodiments, systems may avoid terrestrial reuse of frequencies within agiven satellite cell that are being used within the given satellite cellfor satellite communications. Stated differently, in some embodiments,only frequencies used by other satellite cells may be candidates forterrestrial reuse within a given satellite cell and beam-to-beam spatialisolation that is provided by the satellite system may be relied upon toreduce or minimize a level of interference from the terrestrialoperations into the satellite operations. In contrast, other embodimentsof the invention can use an interference reducer to allow allfrequencies assigned to a satellite cell to be used terrestrially andfor satellite radiotelephone communications.

Embodiments according to FIG. 1 may arise from a realization that thereturn link signal from the second radiotelephone 120 b at f_(U)generally will be received and processed by the ancillary terrestrialcomponent 140 much earlier relative to the time when it will arrive atthe satellite gateway 160 from the space-based component 110 via theinterference path 150. Accordingly, the interference signal at thesatellite gateway 160 b can be at least partially canceled. Thus, asshown in FIG. 1, an interference cancellation signal, such as, forexample, a demodulated and/or regenerated received ancillary terrestrialcomponent signal, can be sent to the satellite gateway 160 b by theinterference reducer 170 a at the ancillary terrestrial component 140,for example using link 142. In the interference reducer 170 b at thegateway 160 b, a weighted (in amplitude and/or phase) replica of thesignal may be formed using, for example, adaptive transversal filtertechniques that are well known to those having skill in the art. Then, atransversal filter output signal may be subtracted from the aggregatereceived satellite signal at frequency f_(U) that contains desired aswell as interference signals. Thus, the interference cancellation neednot degrade the signal-to-noise ratio of the desired signal at thegateway 160, in that a regenerated (noise-free) terrestrial signal, forexample, as regenerated by the ancillary terrestrial component 140, canbe used to perform interference suppression.

FIG. 2 is a block diagram of embodiments of adaptive interferencecancellers that may be located in the ancillary terrestrial component140, in the gateway 160, and/or in another component of the cellularradiotelephone system 100. As shown in FIG. 2, one or more controlalgorithms 204, known to those having skill in the art, may be used toadaptively adjust the coefficients of a plurality of transversal filters202 a-202 n. Adaptive algorithms, such as Least Mean Squared Error(LMSE), Recursive Least Squares (RLS) Kalman, Fast Kalman, Zero Forcingand/or various combinations thereof or other techniques may be used. Itwill be understood by those having skill in the art that thearchitecture of FIG. 2 may be used with, for example, an LMSE algorithm.However, it also will be understood by those having skill in the artthat conventional architectural modifications may be made to facilitateother control algorithms such as Zero Forcing. It will also beunderstood by those of skill in the art that although FIG. 2 illustratesa decision-directed approach, the control algorithm(s) 204 may not relyon decisions but may instead use a priori known to the receiverinformation that may be included and/or provided by a desired signalwaveform component, such as, for example, a pre-amble and/or a mid-ambledata sequence and/or a pilot signal. In some embodiments, the controlalgorithm(s) 204 may use both receiver decisions (as illustrated in FIG.2) and a priori known to the receiver information that may be includedin the desired signal waveform.

Some embodiments of the present invention also may arise fromrealization that systems/methods as shown in FIG. 1 may employ a networkof hundreds, thousands or tens of thousands of ancillary terrestrialcomponents 140 and one or more space-based components 110 that areconfigured to communicate with thousands, tens of thousands, hundreds ofthousands or more of first radiotelephones 120 a in satellite mode andsecond radiotelephones 120 b in terrestrial mode. In such large scalesystems, it may be burdensome, costly and/or otherwise undesirable toprovide interference reduction for all signals generated by largenumbers of the first and second radiotelephones 120 a and 120 b,respectively. Accordingly, some embodiments of the present invention canprovide prefiltering that is associated with the interference reducer170 a and/or 170 b. Prefiltering methods and/or systems as describedbelow may be provided at least partly in the interference reducer 170 ain an ancillary terrestrial component electronic system 140 b, at leastpartially in the interference reducer 170 b in the gateway electronicssystem 160 b and/or at least partially separate therefrom. The prefilteris responsive to the signals that are generated and/or received by theancillary terrestrial components 140 based on communications with theplurality of radiotelephones 120 b in terrestrial mode, to prefilterselected signals from the second plurality of radiotelephones 120 b, sothat they are not used for interference reduction purposes. Accordingly,only selected terrestrially reused satellite frequency signals are usedto reduce potential interference. The load on the adaptive interferencecanceller, such as the adaptive interference canceller of FIG. 2, and/orthe dimensionality (n) thereof, may thereby be reduced.

FIG. 3 is a flowchart of operations that may be performed by aninterference reducer including a prefilter, according to someembodiments of the present invention. These operations may be performedby the interference reducer 170 a and/or 170 b of FIG. 1, or theseoperations may be provided at least partially separate therefrom.

In particular, referring to FIG. 3, at Block 310, a prefilteringfunction is applied to the signals using frequency f′_(U) that arereceived from the second radiotelephones 120 b in terrestrial mode atthe ancillary terrestrial component(s) 140, so that only selected onesof these signals are applied to reduce interference at Block 320.

Many techniques may be used to prefilter the signals. For example, insome embodiments, randomly or pseudo-randomly selected signals usingfrequency f′_(U) or a percentage of the signals from the secondradiotelephones 120 b based on location measures of the radiotelephones120 b, may be prefiltered and not used for interference cancellation.However, in other embodiments, signals are prefiltered based on alikelihood, or maximum likelihood, that these signals will not causeinterference with the return link signals f_(U) from the firstradiotelephones 120 a in satellite mode. Embodiments of such aprefiltering technique are described, for example, in FIG. 4.

Referring now to FIG. 4, as shown at Block 410, prefiltering may beperformed based on a measure of a signal strength of a satellite signalf_(D) that is received by a second radiotelephone 120 b that isoperating in terrestrial mode. In particular, it has been recognizedaccording to some embodiments of the present invention that, in orderfor a second radiotelephone 120 b to create a substantive potentialinterference path 150, the radiotelephone's signal must be able to reachthe space-based component 110 at, or above, a predetermined strength.Accordingly, prefiltering of Block 310 of FIG. 3 may be performed basedon a measure of the strength of the satellite signal that is received bya second radiotelephone 120 b, at Block 410 of FIG. 4. The lower themeasure of the strength of the satellite signal, the less likely it maybe that sufficient signal from the second radiotelephone will reach thespace-based component 110 and create interference.

In some embodiments, the second radiotelephones 120 b that are interrestrial mode can measure one or more components of a downlink(forward link) signal from the space-based component 110 that arereceived at the second radiotelephones 120 b. In some embodiments, oneor more of the control channels that are received in the satellitedownlink are measured. In other embodiments, one or more forward linktraffic channels of the satellite downlink are measured. Combinationsand subcombinations of control and/or traffic channels also may bemeasured. Moreover, as used herein, a measure of signal strengthincludes a received signal strength and/or a measure of received signalstrength such as a quality (bit-error-rate) of the downlink satellitecontrol channel and/or traffic channel.

This measure of strength of the satellite downlink signal(s) may beprovided by the second radiotelephone(s) 120 b to the associatedancillary terrestrial component(s) 140 as part, for example, of theuplink (return link) signal f′_(U) from the second radiotelephone(s) 120b to the associated ancillary terrestrial component(s) 140 a (i.e.,in-band signaling). Alternatively, the downlink satellite signal itself,or a component thereof, may be transferred from the secondradiotelephone(s) 120 b to the ancillary terrestrial component(s) 140,and a measure of signal strength may be derived at the interferencereducer 170 a and/or 170 b. In still other embodiments, the measure ofsignal strength, the downlink signal and/or a component thereof, may betransferred to the interference reducer 170 a and/or 170 b via thespace-based component 110.

In any event, the prefiltering system/method receives a measure of thestrength of the satellite signal at Block 410. Then, at Block 420, adetermination is made as to whether this strength exceeds a threshold.In some embodiments, the determination is made following an integration(smoothing) period during which an average measure of satellite receivedsignal is estimated by, for example, a second radiotelephone 120 b. Itwill be understood that the threshold can be a static and/or dynamicthreshold that may vary, for example, as the number of secondradiotelephones 120 b increases or decreases. It will also be understoodthat the threshold can depend on an interference monitoring systemand/or method such as, for example, those described in the above citedPublished U.S. Patent Application Nos. US 2003/0054814 to Karabinis etal., entitled Systems and Methods for Monitoring Terrestrially ReusedSatellite Frequencies to Reduce Potential Interference; and/or US2003/0073436 to Karabinis et al., entitled Additional Systems andMethods for Monitoring Terrestrially Reused Satellite Frequencies toReduce Potential Interference. As shown at Block 420, if the satellitedownlink signal strength as measured by a given second radiotelephone120 b exceeds the threshold, then a measure of the signal that isradiated by that given second radiotelephone 120 b in order tocommunicate with the ancillary terrestrial component 140 is provided tothe interference reducer, so that interference may be reduced at Block320. If not, then the signal radiated by the given second radiotelephone120 b in order to communicate with the ancillary terrestrial component140 may be “filtered-out” and not be provided to the interferencereducer to be used for interference reducing, thereby reducing a loadingof the interference reducer.

Accordingly, prefiltering is used to selectively determine whether ornot an uplink signal from a radiotelephone that uses and/or reuses asatellite-band frequency is used for interferencereduction/cancellation. In some embodiments, if the uplink signal willnot contribute significantly to interference at the space-basedcomponent, the uplink signal may be discarded (prefiltered) and not usedfor interference reduction. A loading and/or complexity on theinterference canceller may thereby be reduced, while still maintainingacceptable levels of interference reduction.

In some embodiments, the signals received by ATC 140 that satisfy aprefiltering requirement (such as the prefiltering requirement 420 ofFIG. 4) may be sent to the interference canceller (interference reducer)before and/or after demodulation, de-spreading and/or regeneration bythe ATC 140 and/or by any other infrastructure element(s) operativelyconnected to ATC 140. In other embodiments, a signal that is received byATC 140 and satisfies a prefiltering requirement (such as theprefiltering requirement 420 of FIG. 4) may be de-spread and regeneratedby ATC 140 and/or by any other infrastructure element(s) operativelyconnected to ATC 140, and a regenerated measure of the signal may bere-spread before it is used by the interference canceller (interferencereducer). The re-spreading may take place at the ATC 140 and/or at anyother infrastructure element(s) operatively connected with ATC 140, atgateway 160 b, and/or at the interference canceller (interferencereducer). The re-spreading can comprise forming a signal that isidentical (or substantially identical) at the chip level and/or at thesymbol level, to a signal that has been transmitted by a radioterminalcommunicating with ATC 140 and/or SBC 110. In some embodiments, such asin embodiments relating to CDMA systems and methods, the interferencecanceller 170 a, 170 b (interference reducer) may be operativelyconfigured to process an input signal, such as input signal 142, at achipping rate. In other embodiments, the interference canceller(interference reducer) may be operatively configured to process an inputsignal, such as input signal 142, at a symbol rate (after de-spreadinghas occurred). It will be understood by those of skill in the art, thatthe interference canceller (interference reducer) of FIG. 2 relates to adata-directed embodiment in that the “Error” quantity is formed by usingthe output of the “decision making stage.” In other embodiments, wherean a priori known to the receiver transmitted data sequence and/or chipsequence is available (such as a “training sequence” and/or a “pilotsequence”) the a priori known sequence may be used by the interferencecanceller (interference reducer) instead of, and/or in combination with,the output of the “decision making stage” to derive an error quantityand/or an error sequence.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

1. A satellite radiotelephone system comprising: a space-based componentthat is configured to receive wireless communications from a pluralityof first radiotelephones in a satellite footprint over a satelliteradiotelephone frequency band; an ancillary terrestrial network that isconfigured to receive/transmit wireless communications from/to aplurality of second radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band, the space-based component alsoreceiving the wireless communications from the second radiotelephonesand/or the ancillary terrestrial network in the satellite footprint overthe satellite radiotelephone frequency band as interference along withthe wireless communications that are received from the firstradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band; and an interference reducer that isresponsive to the space-based component and to the ancillary terrestrialnetwork, and that is configured to reduce the interference in thewireless communications that are received by the space-based componentfrom the first radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band, using as an input to theinterference reducer, selected wireless communications that are receivedby the ancillary terrestrial network from selected ones of the secondradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band and/or selected wireless communicationsthat are transmitted by the ancillary terrestrial network to selectedones of the second radiotelephones, so as to reduce a load on theinterference reducer compared to using as an input to the interferencereducer, all the wireless communications that are received by theancillary terrestrial network from the second radiotelephones and/or allthe wireless communications that are transmitted by the ancillaryterrestrial network to the second radiotelephones.
 2. A satelliteradiotelephone system according to claim 1 wherein the interferencereducer comprises a prefilter that is configured to determine theselected ones of the second radiotelephones.
 3. A satelliteradiotelephone system according to claim 2 wherein the prefilter isconfigured to determine the selected ones of the second radiotelephonesbased on a measure of signal strength of wireless signals that arereceived by the plurality of second radiotelephones from the space-basedcomponent.
 4. A satellite radiotelephone system according to claim 3 incombination with the plurality of second radiotelephones wherein thesecond radiotelephones are configured to transmit to the ancillaryterrestrial network and/or the space-based component, the measure ofsignal strength of wireless signals that are received by the pluralityof second radiotelephones from the space-based component.
 5. A satelliteradiotelephone system according to claim 3 wherein the prefilter isconfigured to determine the selected ones of the second radiotelephonesbased on a measure of signal strength of wireless signals that arereceived by the plurality of second radiotelephones from the space-basedcomponent exceeding a fixed and/or variable threshold.
 6. A satelliteradiotelephone system according to claim 1 wherein the interferencereducer comprises an adaptive interference reducer.
 7. A satelliteradiotelephone system according to claim 1 further comprising a gatewaythat communicates with the space-based component and with the ancillaryterrestrial network and wherein the interference reducer is at leastpartially included in the gateway.
 8. An interference reducer for asatellite radiotelephone system, the satellite radiotelephone systemcomprising a space-based component that is configured to receivewireless communications from a plurality of first radiotelephones in asatellite footprint over a satellite radiotelephone frequency band andan ancillary terrestrial network that is configured to receive wirelesscommunications from a plurality of second radiotelephones in thesatellite footprint over the satellite radiotelephone frequency bandand/or transmit wireless communications to the plurality of secondradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band, the space-based component also receivingthe wireless communications from the second radiotelephones and/or fromthe ancillary terrestrial network in the satellite footprint over thesatellite radiotelephone frequency band as interference along with thewireless communications that are received from the first radiotelephonesin the satellite footprint over the satellite radiotelephone frequencyband, the interference reducer comprising: an electronics system that isresponsive to the space-based component and to the ancillary terrestrialnetwork, and that is configured to reduce the interference in thewireless communications that are received by the space-based componentfrom the first radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band, using as an input to theinterface reducer, selected wireless communications that are received bythe ancillary terrestrial network from selected ones of the secondradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band and/or selected wireless communicationsthat are transmitted by the ancillary terrestrial network to selectedones of the second radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band, so as to reduce a load on theinterference reducer compared to using as an input to the interferencereducer, all the wireless communications that are received by theancillary terrestrial network from the second radiotelephones and/or allthe wireless communications that are transmitted by the ancillaryterrestrial network to the second radiotelephones.
 9. An interferencereducer according to claim 8 further comprising: a prefilter that isconfigured to determine the selected ones of the second radiotelephones.10. An interference reducer according to claim 9 wherein the prefilteris configured to determine the selected ones of the secondradiotelephones based on a measure of signal strength of wirelesssignals that are received by the plurality of second radiotelephonesfrom the space-based component.
 11. An interference reducer according toclaim 10 wherein the interference reducer is further configured toreceive, from the plurality of second radiotelephones via the ancillaryterrestrial network and/or the space-based component, the measure ofsignal strength of wireless signals that are received by the pluralityof second radiotelephones from the space-based component.
 12. Aninterference reducer according to claim 10 wherein the prefilter isconfigured to determine the selected ones of the second radiotelephonesbased on a measure of signal strength of wireless signals that arereceived by the plurality of second radiotelephones from the space-basedcomponent exceeding a fixed and/or variable threshold.
 13. Aninterference reducer according to claim 8 wherein the interferencereducer comprises an adaptive interference reducer.
 14. An interferencereducer according to claim 8 wherein the satellite radiotelephone systemfurther comprises a gateway that communicates with the space-basedcomponent and with the ancillary terrestrial network and wherein theinterference reducer is at least partially included in the gateway. 15.An ancillary terrestrial network for a satellite radiotelephone system,the satellite radiotelephone system comprising a space-based componentthat is configured to receive wireless communications from a pluralityof first radiotelephones in a satellite footprint over a satelliteradiotelephone frequency band, the ancillary terrestrial networkcomprising: a plurality of ancillary terrestrial components that areconfigured to receive/transmit wireless communications from/to aplurality of second radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band, the space-based component alsoreceiving the wireless communications from the second radiotelephonesand/or the ancillary terrestrial network in the satellite footprint overthe satellite radiotelephone frequency band as interference along withthe wireless communications that are received from the firstradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band; the satellite radiotelephone systemfurther comprising an interference reducer that is responsive to thespace-based component and to the ancillary terrestrial network, and thatis configured to reduce the interference in the wireless communicationsthat are received by the space-based component from the firstradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band, using as an input to the interferencereducer, selected wireless communications that are received by theancillary terrestrial network from selected ones of the secondradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band and/or selected wireless communicationsthat are transmitted by the ancillary terrestrial network to selectedones of the second radiotelephones, so as to reduce a load on theinterference reducer compared to using as an input to the interferencereducer, all the wireless communications that are received by theancillary terrestrial network from the second radiotelephones and/or allthe wireless communications that are transmitted by the ancillaryterrestrial network to the second radiotelephones; and the ancillaryterrestrial network being further configured to transmit, to theinterference reducer, a measure of signal strength of wireless signalsthat are received by the plurality of second radiotelephones from thespace-based component.
 16. An ancillary terrestrial network according toclaim 15 wherein the interference reducer is at least partially includedin the ancillary terrestrial network.
 17. A satellite radiotelephonecommunication method comprising: receiving wireless communications at aspace-based component from a plurality of first radiotelephones in asatellite footprint over a satellite radiotelephone frequency band;receiving/transmitting wireless communications at an ancillaryterrestrial network from/to a plurality of second radiotelephones in thesatellite footprint over the satellite radiotelephone frequency band,the space-based component also receiving the wireless communicationsfrom the second radiotelephones and/or the ancillary terrestrial networkin the satellite footprint over the satellite radiotelephone frequencyband as interference along with the wireless communications that arereceived from the first radiotelephones in the satellite footprint overthe satellite radiotelephone frequency band; and reducing theinterference in the wireless communications that are received by thespace-based component from the first radiotelephones in the satellitefootprint over the satellite radiotelephone frequency band, using as aninput to the reducing, selected wireless communications that arereceived by the ancillary terrestrial network from selected ones of thesecond radiotelephones in the satellite footprint over the satelliteradiotelephone frequency band and/or selected wireless communicationsthat are transmitted by the ancillary terrestrial network to selectedones of the second radiotelephones, so as to reduce a load on thereducing compared to using as an input to the reducing, all the wirelesscommunications that are received by the ancillary terrestrial networkfrom the second radiotelephones and/or all the wireless communicationsthat are transmitted by the ancillary terrestrial network to the secondradiotelephones.
 18. A method according to claim 17 wherein reducing theinterference comprises prefiltering to determine the selected ones ofthe second radiotelephones.
 19. A method according to claim 18 whereinprefiltering comprises determining the selected ones of the secondradiotelephones based on a measure of signal strength of wirelesssignals that are received by the plurality of second radiotelephonesfrom the space-based component.
 20. A method according to claim 19further comprising: transmitting from the second radiotelephones to theancillary terrestrial network and/or the space-based component, themeasure of signal strength of wireless signals that are received by theplurality of second radiotelephones from the space-based component. 21.A method according to claim 19 wherein prefiltering comprisesdetermining the selected ones of the second radiotelephones based on ameasure of signal strength of wireless signals that are received by theplurality of second radiotelephones from the space-based componentexceeding a fixed and/or variable threshold.
 22. A method according toclaim 17 wherein reducing the interference comprises performing adaptiveinterference reducing.
 23. A method according to claim 17 furthercomprising a gateway that communicates with the space-based componentand with the ancillary terrestrial network and wherein reducing theinterference is at least partially performed in the gateway.
 24. Aninterference reducing method for a satellite radiotelephone system, thesatellite radiotelephone system comprising a space-based component thatis configured to receive wireless communications from a plurality offirst radiotelephones in a satellite footprint over a satelliteradiotelephone frequency band and an ancillary terrestrial network thatis configured to receive wireless communications from a plurality ofsecond radiotelephones in the satellite footprint over the satelliteradiotelephone frequency band and/or transmit wireless communications tothe plurality of second radiotelephones in the satellite footprint overthe satellite radiotelephone frequency band, the space-based componentalso receiving the wireless communications from the secondradiotelephones and/or from the ancillary terrestrial network in thesatellite footprint over the satellite radiotelephone frequency band asinterference along with the wireless communications that are receivedfrom the first radiotelephones in the satellite footprint over thesatellite radiotelephone frequency band, the interference reducingmethod comprising: reducing the interference in the wirelesscommunications that are received by the space-based component from thefirst radiotelephones in the satellite footprint over the satelliteradiotelephone frequency band, using as an input to the reducing,selected wireless communications that are received by the ancillaryterrestrial network from selected ones of the second radiotelephones inthe satellite footprint over the satellite radiotelephone frequency bandand/or selected wireless communications that are transmitted by theancillary terrestrial network to selected ones of the secondradiotelephones in the satellite footprint over the satelliteradiotelephone frequency band, so as to reduce a load on the reducingcompared to using as an input to the reducing, all the wirelesscommunications that are received by the ancillary terrestrial networkfrom the second radiotelephones and/or all the wireless communicationsthat are transmitted by the ancillary terrestrial network to the secondradiotelephones.
 25. A method according to claim 24 wherein reducing theinterference comprises prefiltering to determine the selected ones ofthe second radiotelephones.
 26. A method according to claim 25 whereinprefiltering comprises determining the selected ones of the secondradiotelephones based on a measure of signal strength of wirelesssignals that are received by the plurality of second radiotelephonesfrom the space-based component.
 27. A method according to claim 24further comprising receiving from the plurality of secondradiotelephones via the ancillary terrestrial network and/or thespace-based component, the measure of signal strength of wirelesssignals that are received by the plurality of second radiotelephonesfrom the space-based component.
 28. A method according to claim 24wherein prefiltering comprises determining the selected ones of thesecond radiotelephones based on a measure of signal strength of wirelesssignals that are received by the plurality of second radiotelephonesfrom the space-based component exceeding a fixed and/or variablethreshold.
 29. A method according to claim 24 wherein reducing theinterference comprises performing adaptive interference reducing.
 30. Amethod according to claim 24 further comprises a gateway thatcommunicates with the space-based component and with the ancillaryterrestrial network and wherein reducing the interference is at leastpartially performed in the gateway.